Saturday, October 29, 2011

The why of water bouncing balls

via xrXiv.org

A team of researchers has figured out why a water bouncing ball, known as a Waboba, bounces across the water so well.

By John Roach

Some balls bounce on water, and some do it better than others. The best in class is the trademarked Waboba, which stands for water bouncing ball. And now a team of mechanical engineers has figured out why the Waboba works so well.

The team led by Michael Wright at Brigham Young University's Splash Lab in Provo, Utah, did this by attempting to skip three types of balls across the water, videotaping the activity, and analyzing the footage. Their results are posted on arXiv.org, including a video that explains it all.


The tests involved a?SuperBall, a racquetball and, of course, the Waboba. Here's the gist of what they found:

The SuperBall, which is solid, stiff, and has a large ratio of mass relative to its size, plunged underwater even when thrown at a shallow angle, as we learned to do when skipping stones. It doesn't bounce.

The racquetball, which is hollow and has a much lower mass ratio, creates a small cavity and then rebounds quickly, but it kicks up a wave that it has to bust through, which slows it down. It bounces a little.

The Waboba skips supremely across the water like a child let out of school for the summer. Why such skipping prowess??

The team explains that it flattens inside the cavity it creates and moves through the cavity like a skipping stone, which, the video shows, planes out of the cavity it creates. Notice, too, that there's little surrounding wave for the Waboba to break through, allowing it to bounce more easily.

While similar to a skipping stone, the researchers note that the Waboba makes for a more user-friendly toy.

"While some skill is needed throw the Waboba across the pond, it adapts to each skip because of its elastic response whereas the stone must be thrown perfectly in order to gain the best skipping advantage," the researchers conclude.

This is cool and all, but why do this type of research? The video doesn't say, but, as Technology Review notes: "The fact that one of the team is with the Naval Undersea Warfare Center in Newport might offer a clue."

More on skipping across the water:


John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

Disposable computers for hurling into infernos, underwater robots that team up for search and rescue, and other new tools are coming to the aid of emergency responders during calamities.

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Source: http://futureoftech.msnbc.msn.com/_news/2011/10/27/8508003-the-why-of-water-bouncing-balls

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